Life-history characteristics of the yakka skink, Egernia rugosa, indicate long-term social structure.

One lineage of squamates, the Egernia group, has received particular study due to stable aggregations identified in many of the species. Egernia rugosa is a large, terrestrial, viviparous skink and has been reported living communally. To investigate whether this species lives in social aggregations, we examined life-history characteristics in one population within the Mulga Lands bioregion of south-west Queensland. We found this skink used both active and inactive rabbit burrows. Parturition occurred in January/February and took several days to complete, with a mean litter size of 2.4 and a mean snout-vent length (SVL) of 84.5 mm. Six subadult age cohorts were identified. Juveniles took at least five years to reach sexual maturity and lizards had a life expectancy of >12 years. Lizards were found clustered in aggregations of up to 21 individuals (mean = 7.21) of multiple ages. An average of 50% (range = 31-67%) of all individuals within each of the age cohorts were located at their original location for two or more seasons. Dispersal was recorded for older subadult lizards. These characteristics support the hypothesis that E. rugosa aggregations comprise long-term family units; however, genetic analysis would be needed to confirm kin-based associations.